Dual period gyro-compass



Nov. 5, 1957 L. F. CARTER DUAL PERIOD GYRO-COMPASS 5 Sheets-Sheet 1 Filed April 25, 1955 I INVENTOR. LESLIE FZ CARTE Nov. 5, 1957 Filed April 25, 1953 N i w L. F. CARTER DUAL. PERIOD GYRO-COMPAFS 3 Sheets-Sheet 2 l lu LESL/ ECZQQTU? Nov. 5,1957 L. F. CARTER 2,311,736

DUAL PERIOD GYRO-COMPASS Filed April 25, 1953 s Sheets-Sheet 3 INVENTOR 55m: E CARTER United States Patent H 2,811,786 DUAL PERIOD GYRO-COMPASS Leslie F. Carter, Leonia, N. 1., assignor to Sperry Rand Corporation, a corporation of Delaware Application April 23, 1953, Serial No. 350,634 16 Claims. (Cl. 33--226) This invention relates to gyroscopic compasses now in wide use for ships. As now designed, substantially all ships gyro compasses require on the order of three hours for settling when the initial displacement is 30 or more from the meridian. This long settling time is due to several accepted criteria in design; one, that the compass should be so designed that the normal period of oscillation of the compass about the meridian is about 85 minutes in order to secure the proper ballistic deflection when the ship changes course or speed; and two, the damping factor should be made comparatively low, about 66% in order to minimize the error caused by the damping factor upon change of speed or course of the ship.

According to my invention, I have greatly reduced this long settling time by reducing the standard 85 minute period to half or less than half this period, but I retain the advantages of proper ballistic deflection by restoring the 85 minute period only during the time that the ship is changing speed or course. Also I automatically eliminate the damper during course or speed changes and thereby eliminate the damping acceleration error. Since the damper is not in use at the time it might cause an error, I also increase the damping factor to 80 or 90% or more. By these improvements, I have been able to reduce the time taken by my compass to settle on the meridian from 30 or more displacement to less than one hour instead of about three hours and still retain the full advantages of the ballistic deflection.

This application is a continuation-in-part of my forfeited prior application 95,895, filed May 28, 1949, for Dual Period Gyro Compass, and also of my prior application, now Patent No. 2,510,068, dated June 6, 1950, for Gyrocompass.

According to my invention, I have also simplified and improved the ballistic control of gyro compasses, whereby ordinary pivoted masses may be employed instead of the mercury ballistic heretofore used on gyro compasses, and without introducing intercardinal rolling errors.

Referring to the drawings, several forms of the invention are shown, in which t Fig. 1 is a south elevation partly in section of a gyrocompass constructed in accordance with my invention, known parts being omitted for the sake of simplicity;

, Fig. 2 is a side elevation of the same partly in section;

Fig. 3 is a south elevation of a gyro-compass showing a modified form of the invention;

Fig. 4 is a side elevation of the same partly in section;

Fig. 5 is a sectional detail showing the damping means employed for Figs. 3 and 4;

Fig. 6 is a sectional detail showing a modified form of damping means employed for Figs. 3 and 4;

Fig. 7 is a side elevation partly in section of another modification in which the gravitational factors are pendulums pivoted on the gyro casing; and

Fig. 8 is a south elevation of the same.

The type of gyro-compass to which my invention is shown as applied is illustrated in my prior application for Gyro-Compasses, now Patent No. 2,510,068, dated June p 2,811,786 Patented Nov. 5, 1957 "ice 6, 1950. As shown this compass consists essentially of a vertical ring 1, mounted for freedom about a vertical axis 22 in a phantom or follow-up ring 3 which is oriented from a suitable form of pick-oflf 4 between the two rings which actuates an azimuth motor 5 to orient the ring 3. The phantom ring in turn is supported for orientation by thrust and guide bearings 10 and 11 in a supporting spider 12 which is gimbal mounted on the ship. The gyro rotor casing 6 is mounted for oscillation about a horizontal axis 7 within the vertical ring in neutral equilibrium, the spin axis 8 of the rotor 9 being perpendicular to the axis 7.

To impart meridian-seeking properties, I have shown as a gravitational factor a mass 13 pivoted on the gyro casing 6. The mass may be either pendulously or antipendulously pivoted so that its center of gravity lies in the same horizontal plane as horizontal axis 7-7 and is aligned with the spin axis 8 of the rotor 9 whereby the mass tends to shift laterally substantially parallel to the spin axis of the rotor upon tilt of the rotor case about axis 7 under the action of gravity or upon the application of any other acceleration force having a north-south component. When so shifted, gravity acting on the eccentric mass will impart meridian seeking properties. As shown, the mass is anti-pendulously supported on parallel leaf springs 14 and 15 so that it tends to fall toward the low side of the compass. The springs 14 and 15 support ing the mass 13 are shown as semicircular leaf springs secured at the bottom to an arm 19 extending from the gyro case 6 and secured at their tops to each side of the mass 13. The movement of the mass upon tilt of the compass is therefore substantially parallel to the spin axis 8. The mass is so designed that taken alone it would cause the normal period of the gyro-compass to be substantially the standard period of about minutes.

The mass also preferably controls an additional torque applying device which normally gives the compass a much shorter period. Also, at the same time, a damping device is brought into action whereby the compass is damped in its oscillations about the meridian.

The lateral movements of the mass are damped as by means of paddles or blades 16 and 16' secured thereto so as to be moved through the damping liquid 17 such as silicone in pots 18 secured to the gyro casing. This damping action is so designed that the mass 13 does not respond to the short period roll and pitch acceleration of the ship (on the order of a few seconds) or at least does not respond in phase with such acceleration so that intercardinal or quadrantal rolling errors are prevented. On the other hand, this damper does not interfere with the action of longer period acceleration forces due to the change in speed or course thereon (on the order of a minute or two) or to the much longer period of oscillation about the meridian (35 minutes). Said damper, therefore, may be termed a time delay device. Since the amount of viscous damping of the pendulous factor or mass 13 itself is somewhat critical, I prefer to adjustably mount the paddles about their vertical axes within the damping fluid. The paddles may be made in streamlined form (Fig. 5) and their supporting stems 30 are adjustable to present more or less of the' fiat sides in the direction of movement of the paddle. Preferably, the paddles are equally and oppositely adjusted so as to avoid any twisting of mass 13 on its leaf spring support. Scales 31 and lock nuts 32 may be provided for this purpose.

Also secured to said mass are a pair of arcuate baflles 21, 22 each having an arcuate slot 23 therein normally adapted to overlie from opposite sides about half of the elongated air jet producing slots 24, 24 in cylindrical extension 25 from the gyro case. Air is discharged through said slots 24, 24 under pressure, such as created by the rotation of the gyro wheel, or by impeller 25 connected to the shaft of the rotor. the baffles usually bisect the slots 24, 24' but on opposite sides of the vertical so that the reaction of the upwardly projected jet is normally cancelled by the downwardly projected jet; but any lateral shifting of plates 21 and 22 will further open one jet and start to close the other. Thus, assuming the compass tilts clockwise in Fig. 2, the upward jet becomes less baffled and its reaction greater than the more battled lower jet so as to add this unbalanced force or torque to that of a displaced mass 13. This will result, therefore, in reducing the period of the compass by an amount proportional to the relation between torque due to the mass 13 and that due to the 'air jets, For example, if the air blast gave a torque substantially equal to that of the mass 13 for each increment of tilt (within limits) the period of the compass would be halved. In normal meridian-seeking action, this is the behavior of the compass.

If, however, the ship turns, the centrifugal force acting on the mass 13 usually causes a larger lateral movement of the baflles 21, 22, so that apertures 23, 23' are both displaced beyond the jets 24, 24 thus cutting off the air reaction. At this time, therefore, the only meridian seeking torque affecting the gyro is that due to the mass 13 and the compass has the greater or 85 minute period.

Also, I prefer to make use of the same air jets to damp the compass about the meridian by giving them an inclination represented by the angle b in Fig. 1 so as to give them a reaction about the vertical axis to reduce the tilt. Since, however, the air jets are cut off on acceleration of the ship to lengthen the period, the damping action is likewise cut off during turn or change of speed of the ship, thereby eliminating this source of error.

Because of this, I am enabled to increase the damping factor beyond that usually employed so as to make the compass substantially deadbeat, thus further reducing the time of settling. Another form the invention may assume is shown in Figs. 3 and 4. In this form, two spaced masses 13 and 35 are shown as spring mounted on opposite sides of the rotor case by means similar to that shown in Fig. 1. Each mass is damped by paddles dipping into a viscous fluid Within pots 18', 26 as before but in this case the viscous action of one of the dampers is made very much greater than that of the other. The viscosity of the damper 18 on mass 13 may be made about the same as that of the dainper'18, 18' in Fig. 1 so that the mass, while not responding to roll and pitch of the ship, will respond to changes in speed and course as well as earth induced tilts. The damper 26, on the other hand, is made stiff to such a degree that it is responsive only to the relatively slow earth induced tilt of the gyro, and is not responsive to the turn or speed acceleration. Hence, during acceleration the other mass 13' functions alone for introducing the heading correction due to ballistic deflection at which time the compass will have its proper 85 minute period. When the compass is settling on the meridian, however, the ballistic 35 is also adding its torque to that of the ballistic 13' giving the compass a shorter period.

I therefore prefer to actuate the meridional oscillation damper for this type compass only from the ballistic 35. The damper is shown as a pair of air jets 40 which emerge from the extension on the gyro case 25 in an east-west direction and are normally bisected by baffles 41 secured to the shiftable mass 35. Displacement of the mass resulting from gyro tilt cases one jet to gradually close and the opposite jet to gradually open applying a damping torque about the vertical axis proportional to gyro tilt. Since the ballistic 35 is not responsive to speed and course changes, therefore it follows that the damping torque also remains unchanged under these conditions avoiding the damping acceleration error.

The jet torque type cutoff baffle such as shown in Fig. 2 may alternatively be employed in the form of the inven- The slots 23, 23 in tion shown in Figs. 4 and 5 if desired, this modification being illustrated by Fig. 6 in which this type of baffle is shown as mounted on the mass 35. It is interesting to note, however, that in this case, while the less viscous damper could remain on mass 13' with the highly viscous damper on the mass 35, these dampers should preferably be interchanged in this form of the invention with the very viscous damper on mass 13' and the less viscous damper on the mass The baffles 41' in this case resemble the slotted baffles 21, 22 of Fig. 1 in that each has a slot therein half overlying ports or jets 40. The jets will then become ineffective when the mass is moved an increased amount to close both ports entirely as explained in connection with Fig. 1.

In Figs. 7 and 8, my invention is shown as applied to a gyro compass in which the gravitational factor supplied by the pendulum or pendulums is pivoted on the gyro case above the horizontal axis of support so that normally the center of gravity of the system and pendulums is in the same horizontal plane as the center of support. Upon tilt of the gyro, however, the pendulum or pendulums remain vertical so that the center of gravity of the whole is shifted to the low side, so that the gyro behaves as an anti-pendulous gyro compass, as do the forms previously described. Like parts corresponding to the main forms of the invention are correspondingly numbered in Figs. 7 and 8 and the description thereof need not be repeated.

Preferably, I employ two pendulums 50, one pivoted on each side of the gyro case above the horizonal east-west axis of the compass 7, 7'. Both pendulums are damped by having vanes 51 thereon which dip intoa viscous liquid 52 in liquid containers 53, 53 secured to the gyro case near the bottom. In this instance, the vanes have their shorter dimension in the direction of movement thereof through the liquid so as to avoid the piling up of the liquid on one side as the vane is moved therethrough. As in Figs. 3 and 4, the viscosity of the liquid in the container 53 is preferably made much greater than that in the container 53' so that relative movement of the pendulum 50 and rotor case takes place only on the relatively slow earth induced tilt of the gyroscope and is not responsive to turns or changes in speed. I, therefore, prefer to put the damper 40, 41' on this compass, only on the heavily damped pendulum. This damper may be the same form as shown in Figs. 4 and 5, the damping jets 40' being shown as radial with respect to the pivot 55 of the pendulum 50, since the relative movement between the pendulum and gyro case takes place about said point. 'It is obvious that this form of the invention is also subject to the modification above described with respect to Fig. 6, if so desired.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A dual period gyro-compass having a mass movably mounted on the compass for applying a meredian seeking torque about the horizontal axis thereof, said mass shifting under the influence of gravitational or other acceleration forces, and means brought into action by said shift for normally exerting a meridional torque in addition to said first torque upon a shift of said mass through a predetermined distance but becoming ineflective to exert said extra torque upon further shift of said mass beyond said distance.

2. A dual period gyro-compass as claimed in claim 1 in which said means brought into action by said shift also causes a damping-torque to be applied in addition to the additional meridional torque but which likewise becomes inefiective upon'further shift of said mass.

3. A dual period gyro-compass having two masses separately movably mounted on the compass for applying torques about the horizontal axis thereof, said masses tending to shift under the influence of gravitational or other acceleration forces, damping means for retarding said shift, the damping means for one of said masses being so stiff that said mass is relatively unresponsive to short period acceleration forces such as due to turns or change of speed whereby the period of the compass is lengthened during acceleration.

4. A dual period gyro-compass as claimed in claim 3 having a compass damper brought into action only by the shifting of said one mass, whereby the compass dampmg means is ineffective during short period accelerations, such as due to turns or change of speed of the ship.

5. A dual period gyro-compass as claimed in claim 3 having a compass damper brought into action only by the shifting of the other mass, and means for eliminating the damping action upon shifting of said mass beyond a predetermined amount.

6. A dual period gyro-compass having two means for applying cumulative meridian seeking torques thereto, both of which respond to acceleration forces having a period greater than the short period roll and pitch accelerations and means for rendering ineffective one of said means during the action of acceleration forces characteristic of those due to change of speed or course of the ship, whereby the period is lengthened during changes of speed or course.

7. A dual period gyro-compass as claimed in claim 6 wherein said last-named means includes a time delay device which is unresponsive to acceleration forces having a continuity of on the order of a few minutes.

8. A dual period gyro-compass as claimed in claim 6, said last-named means being effective only in the presence of acceleration forces of much greater magnitude than that due to the gravitational component normally acting on the compass.

9. A dual period gyro-compass having two means for applying cumulative meredian seeking torques thereto, both of which respond to acceleration forces having a period greater than the short period roll and pitch accelerations, means for cutting out one of said means by the action of acceleration forces characteristic of those due to change of speed or course of the ship, normally efiective compass damping means, and means actuated by said cutout means for rendering said damping means ineffective.

10. A dual period gyro-compass having two means for applying cumulative meridian seeking torques thereto, and a means for applying a damping torque thereto, all of which respond to acceleration forces having a period greater than that of accelerations due to roll and pitch, but one of said first two means and said damping means being unresponsive to acceleration forces characteristic of those due to change of speed or course of the ship.

11. In a gyroscopic compass, a damper therefor for damping the meridional oscillations thereof, a gravitational factor therefor for imparting meridian-seeking properties thereto which shifts N-S upon tilt of the gyroscope or under the action of acceleration forces having a N-S component, and means responsive to a shift of said factor materially greater than that which normally occurs during a meridian-seeking cycle for reducing the effectiveness of the damper without interfering with the normal action of said factor in imparting meridian-seeking properties to the compass.

12. A gyro-compass for ships and the like comprising a gyroscopic directional element, means pivoting said element in neutral equilibrium on a horizontal axis, a gravitational controller laterally movable N-S thereon in response to tilt of said element about said axis to thereby cause a proportional meridian-seeking torque sutficient to give the compass a period shorter than the usual minute period, and means responsive to displacement of said controller of more than a predetermined amount, such as caused by a turn of the ship, for decreasing said proportional torque sufliciently to increase the period during a turn to the usual period.

13. A gyro-compass for ships and the like comprising a gyroscopic directional element, means pivoting said element in neutral equilibrium on a horizontal axis, a gravitational controller laterally movable N-S thereon in response to tilt of said element about said axis to thereby cause a proportional meridian-seeking torque suflicient to give the compass a period shorter than the usual 85- minute period, means controlled by such movement for also exerting a damping torque on the element, means responsive to displacement of said controller of more than a predetermined amount, such as caused by a turn of the ship, for decreasing said proportional torque sufficiently to increase the period during a turn to the usual period, and means likewise responsive to such increased displacement for also eliminating said damping torqueduring a turn.

14. A gyro-compass for ships and the like comprising a gyroscopic directional element, two-part variable gravitational control means connected thereto to normally exert meridian seeking torques, one of which also exerts damping torques thereon proportional to said meridian seeking torques and sufficient to give the compass a period less than the usual 85-minute period and to strongly damp the same, and means for preventing turns of the ship from causing error including means for rendering that part of said gravitational means controlling the damper insensitive to turns to thereby lengthen the period to 85 minutes whereby correct ballistic deflection is retained during turns and damping error avoided.

15. A gyro compass for ships as claimed in claim 12, in which said gravitational controller comprises two parts, both of which are normally operated to give the compass a period much less than 85 minutes but one of which is rendered inoperative because of lateral acceleration forces such as caused by change of speed or course of the ship, whereby the period at such times is increased to about 85 minutes.

16. A gyro-compass for ships comprising a gyro rotor and rotor case, means pivoting said rotor case and its attached parts in neutral equilibrium about a horizontal axis, a mass pivoted on said case about an axis parallel to but vertically displaced from said horizontal axis and normally having its center of gravity in the plane of said horizontal axis and in line with the spin axis of said rotor, said mass constituting one of said attached parts whereby upon tilt of said case about said axis said mass is displaced to shift the center of gravity of said case in a N-S direction, a viscous damper acting between said mass and case to retard such displacement, the viscosity of said damper being so proportioned as not to interfere with meridian-seeking action and ballistic deflection, but to retard such displacement sufliciently to throw it out of phase with the roll and pitch of the ship thereby preventing intercardinal rolling errors, and other means for damping the slow oscillations of the compass about the meridian.

References Cited in the file of this patent UNITED STATES PATENTS 1,625,361 Henderson Apr. 19, 1927 1,749,059 Bassett Mar. 4, 1930 1,773,411 Thompson Aug. 19, 1930 1,773,412 Thompson Aug. 19, 1930 1,854,869 Thompson Apr. 19, 1932 1,986,807 Gillmor Jan. 8, 1935 2,510,068 Carter June 6, 1950 FOREIGN PATENTS 417,800 Italy Jan. 29, 1947 

